Bromoacetic acid

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2007

Reliability:

1 (reliable without restriction)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2007

Report date:

2006

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Bromoacetic acid

EC Number:

201-175-8

EC Name:

Bromoacetic acid

Cas Number:

79-08-3

Molecular formula:

C2H3BrO2

IUPAC Name:

2-bromoacetic acid

Test material form:

solid: crystalline

Details on test material:

- Name of test material (as cited in study report): Monobromoacetic acid
- Substance type: white to yellow crystals
- Physical state: solid
- Analytical purity: 99.6%
- Purity test date: 99.6%
- Lot/batch No.: S4394760
- Expiration date of the lot/batch: 31 August 2010
- Radiochemical purity (if radiolabelling): 99% (HPLC)
- Specific activity (if radiolabelling): 50 mCi.nmol-1
- Locations of the label (if radiolabelling): <-18°C (storage)
- Expiration date of radiochemical substance (if radiolabelling): 31 January 2006
- Storage condition of test material: ambient temperature, protected from light (non-radiolabeled)

Radiolabelling:

yes

Remarks:

[2-14C]Bromoacetic acid

Test animals

Species:

other: Rat and human

Strain:

other: Rat: Wistar (Crl:(WI)WU BR); Human: not specified except age

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source:
* Rat:
Charles River Deutschland, Sulzfeld, Germany)
* Human:
Donor 1: TNA 20/05, born in 1970, arrival at TNO lab on 12 July 2005
Donor 2: TNA 02/06, born in 1975, arrival at TNO lab on 9 January 2006
Donor 3: TNA 10/06, born in 1974, arrival at TNO lab on 10 April 2006
- Age at study initiation:
* Rat: 7 weeks old

Administration / exposure

Type of coverage:

other: in vitro

Vehicle:

water

Duration of exposure:

8 hours with 16 hours post exposure time

Doses:

- Concentration of test substance: State concentration of test substance in test dose: 77 μg/cm²; 133 μg/cm²; 500 μg/cm²
Note: Skin integrity was determined in a preliminary study, showing that a Bromoacetic acid concentration or 5% in water represents a worst-case
situation. In addition this concentration will lead to a product labelling
as corrosive (R34). Inclusion of that high concentration allows a worstcase estimation of the amount of Bromoacetic acid absorbed through skin.

No. of animals per group:

Not applicable - In vitro system

Control animals:

no

Remarks:

Not applicable

Details on in vitro test system (if applicable):

- Preparation of skin samples:
* Rat:
After the sacrifice of the rat, the dorsal and flank skin of the animal were clipped free of fur by means of electric clippers. After collection, the skin was stored in aluminium foil at <-18°C until use. For rat skin, discs with a diameter of 16 mm were punched out, after which subcutaneous fat was removed with scissors.
* Human:
Human skin membranes were prepared from frozen skin samples. After thawing of the skin, human skin was dermatomed using a Dennatome 25 mm (Nouvag GmbH. Germany) to a recorded thickness of approximately 400 μm.
The exact thickness of all skin membranes was measured with a digimatic micrometer (Mitutoyo Corporation, Japan) and recorded.
- Flow-through diffusion cells:
The skin membranes were placed in 9 mm flow-through automated diffusion cells (PenneGear Inc., Riegelsville, PA, USA). The skin surface temperature was kept at approximately 32°C, at ambient humidity. The actual temperature was recorded at last 4 times: (rat) 32.3 + 0.2 °C; (human) 32.3 °C + 0.3 °C.
- Number of replications: 6 of 3 donors
- Specific activity of test substance:
* Rat: kBq/mL
* Human: kBq/mL
- Volume applied: 10 μL/cm²; 50 μL/cm²
- Sampling time: 0 - 24h after initiation of skin contact, other time points possible

Results and discussion

Signs and symptoms of toxicity:

not specified

Remarks:

See below details on integrity of skin membranes

Dermal irritation:

yes

Remarks:

See below for further details

Total recovery:

* Rat: mean > 90%
* Human: mean > 91%

Percutaneous absorption

Percutaneous absorption 1

Dose:

5% Monobromoacetic acid in water

Parameter:

percentage

Absorption:

43.1 %

Remarks on result:

other: 24h

Remarks:

Rat

Percutaneous absorption 2

Dose:

5% Monobromoacetic acid in water

Parameter:

percentage

Absorption:

83.9 %

Remarks on result:

other: 24h

Remarks:

Human

Percutaneous absorption 3

Dose:

1.33% Monobromoacetic acid in water

Parameter:

percentage

Absorption:

14.4 %

Remarks on result:

other: 24h

Remarks:

Rat

Percutaneous absorption 4

Dose:

1.33% Monobromoacetic acid in water

Parameter:

percentage

Absorption:

55.7 %

Remarks on result:

other: 24h

Remarks:

Human

Percutaneous absorption 5

Dose:

0.77% Monobromoacetic acid in water

Parameter:

percentage

Absorption:

12.7 %

Remarks on result:

other: 24h

Remarks:

Rat

Percutaneous absorption 6

Dose:

0.77% Monobromoacetic acid in water

Parameter:

percentage

Absorption:

44.4 %

Remarks on result:

other: 24h

Remarks:

Human

Any other information on results incl. tables

* Integrity of skin membranes

Prior to the determination of the percutaneous absorption of Bromoacetic acid, the permeation coefficient (Kp) for tritiated water was determined in 26 human and 24 rat skin membranes.

Eighteen human membranes with a Kp value below the cut-off value of 2.5 x 10-3 cm/h and 18 rat membranes below the cut-off value of 3.5 x 10-3 cm/h were selected for the study.

* Dermal irritation

Bromoacetic acid is corrosive; therefore the dose-dependent integrity of the skin membranes was established in a preliminary study TNO report V6764 (A6.2.2/02). At concentrations above 5% in water, Bromoacetic acid is classified as corrosive (R34) i.e. causing irreversible damage to the skin. In the pilot study, 5.28 % Bromoacetic acid in water resulted in a ca. 4-fold increase in the Kp for tritiated water, indicating membranedisturbing properties at this dose level. This group was therefore included as a worst-case.

Applicant's summary and conclusion

Conclusions:

The percutaneous absorption of 14C- Monobromoacelic acid (MBAA) was evaluated at three dose levels on 6 human and rat skin membranes each. Three different human donors (two membranes per donor per group) were used. The exposure time was 8 hours, with 16 hours post·exposure time. When comparing human skin with rat skin, human skin was found to be more permeable for MBAA at all three concentrations tested. Based on total absorption, human skin was 1.3 to 1.7 times more permeable to MBAA compared to rat skin. Based on maximal flux, human skin was 2.5 to 12.3 times more permeable.

Executive summary:

The percutaneous absorption of (14C)Monobromoacelic acid (MBAA) was evaluated at three dose levels on 6 human and rat skin membranes each. Three different human donors (two membranes per donor per group) were used. The exposure time was

8 hours, with 16 hours post-exposure time.

* In human skin, the mean penetration of 4.98 % MBAA in water into the receptor fluid after 24 hours was 417.3 µg.cm-2, which was 83.9 % of the dose applied. The mean maximal flux through human skin at this concentration was 215.6 µg.cm-2.h-1 and the

lag time was 0.5 h. The mean total absorption was 90.6 %.

The mean penetration from a 1.32 % MBAA solution after 24 hours was 71.3 µg.cm-2 (55.7 % of the dose applied). The mean maximal flux was 29.4 µg.cm-2.h-l, the lag time was 1.0 h and the mean total absorption was 70.3 %.

When applied as a 0.76 % solution in water, the mean penetration was 31.5 µg.cm-2 (44.4 % of the dose applied). The mean maximal flux was 7.0 µg.cm-2.h-1 the lag time was 1.0 h and the mean total absorption was 64.5 %.

The mean recovery of MBAA in human skin was over 91 % for all three concentrations tested.

* In rat skin, the mean penetration of 5.00 % MBAA in water into the receptor fluid after 24 hours was 225.1 µg.cm-2, which was 43.1 % of the dose applied. The mean maximal flux at this concentration was 87.8 µg.cm-2.h-1 and the lag time was 0.7 h. The mean

total absorption was 68.5 %. The mean penetration from a 1.33 % MBAA solution after 24 hours was 17.1 µg.cm-2 (14.4 % of the dose applied). The mean maximal flux was 2.4 µg.cm-2,h-1, the lag time was 0.9 h and the mean total absorption was 52.2 %.

When applied as a 0.77 % solution in water, the mean penetration was 8.7 µg.cm-2 (12.7 % of the dose applied). The mean maximal flux was 2.5 Jµg.cm-2.h-l, the lag time was 0.2 h and the mean total absorption was 38.1 %.

The mean recovery of MBAA acid in rat skin was over 90 % at all three concentrations tested.

When comparing human skin with rat skin, human skin was found to be more penneable for MBAA at all three concentrations tested. Based on total absorption (defined as the compound-related radioactivity present in the receptor fluid, the receptor compartment wash and the skin (excluding tape strips)), human skin was 1.3 to 1.7 times more permeable to MBAA compared to rat skin. Based on maximal flux, human skin was 2.5 to 12.3 times more permeable.